User blog:SPCBlackfordCounty995Main/30 PERCENT CHANCE OF SEVERE WEATHER ON SUNDAY...INCLUDES MY FUTURE LIVE STREAM LINK
Day 4-8 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0257 AM CST Thu Jan 19 2017 Valid 221200Z - 271200Z CORRECTED TO ADD MISSING WORD ...DISCUSSION... ...Southeast Atlantic coast Sunday/day 4... Substantial cyclogenesis is expected, generally in the immediate lee of the southern Appalachians, Sunday into Monday morning as a strong mid-upper shortwave trough traverses the Southeast and Gulf basin. There are some differences in the details regarding the cyclogenesis and lingering influences of a lead speed max early in the period. However, the scenario still appears favorable for a squall line to form along or in advance of the synoptic cold front which will then move across parts of FL/GA and the Carolinas. Given an established moist boundary layer across the Gulf basin already, an unstable warm sector appears likely in advance of the cold front. Given weak-moderate buoyancy and very strong low-midlevel vertical shear in the warm sector, there will be the potential for substantial severe weather, especially across parts of GA/FL where instability will be less in question. ...Day 5/Monday and beyond... In the wake of the strong cyclone/cold front, only limited moisture return is expected ahead of another cold front that will approach the Gulf coast days 6-7, along the southern fringe of a positive-tilt upper trough. ..Thompson.. 01/19/2017 Here is the coverage live stream that will start at 7:30AM ET/4:30AM PT on 1/22/2017: January 22, 2017 Severe Weather Event Live Stream (the stream will end at 9:30PM ET/6:30PM PT) Update as of 10:19AM on January 22, 2017: A High Risk of Severe Thunderstorms is now in effect, here is the 1300 day 1 outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0653 AM CST Sun Jan 22 2017 Valid 221300Z - 231200Z ...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS TODAY ACROSS SOUTH GEORGIA...NORTH FLORIDA...AND EXTREME SOUTHEAST ALABAMA... ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS SURROUNDING THE HIGH RISK AREA...FROM CENTRAL FLORIDA TO SOUTH CAROLINA... ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SURROUNDING THE MODERATE RISK AREA...FROM SOUTH FLORIDA TO SOUTHERN NORTH CAROLINA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK AREA... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK AREA IN THE SOUTHEAST STATES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY ACROSS THE CENTRAL CALIFORNIA COAST... ...SUMMARY... A severe thunderstorm and tornado outbreak is expected today across north Florida and south Georgia, with the significant severe threat also expected to extend southward into central Florida and northeastward into South Carolina this evening. ***Significant tornado outbreak expected today across north Florida and south Georgia*** ...Synopsis... An amplifying mid-upper trough over TX/OK this morning will continue eastward to MS/AL by this afternoon. The initial synoptic cyclone near Texarkana will likely be replaced by cyclogenesis today at the triple point of the effective warm front across southern AL, and the eastward-surging cold front/trough from LA/MS. This new cyclone will deepen and move north-northeastward today across AL/GA in association with the strong height falls/ascent within the exit region of a 100-130 kt mid-upper jet. Likewise, very strong deep-layer tropospheric flow is expected within the warm sector, where boundary layer dewpoints in the 65-70 F range and a lingering steep lapse rate plume will support moderate buoyancy. The net result of these factors will be the potential for a significant tornado episode today across north FL into south GA. ...AL/FL/GA today to the Carolinas this evening/tonight... A broken band of severe storms that formed overnight persists this morning across south GA. This convective band was associated with low-level warm advection, as well as an ejecting midlevel trough that is now over north GA and east TN. It is not clear if this convection will weaken this morning, or if it will persist until new thunderstorms begin to form farther to the west across south AL and the FL Panhandle. Regardless the boundary should begin to move northward by midday as cyclogenesis proceeds across AL. Likewise, as the synoptic midlevel trough approaches from the west, strengthening vertical shear is expected within the unstable warm sector. Observational data confirm the most important aspects of the thermodynamic and kinematic profiles, thus confidence is high in the unusual combination of ingredients today. Forecast soundings suggest the potential for MLCAPE of 1000-1500 J/kg, with effective bulk shear in excess of 70 kt, and effective SRH in excess of 300-400 m2/s2. The orientation of deep-layer shear vectors across the cold front/trough will favor broken bands of tornadic supercells. Aside from the ongoing storms across south GA, the severe/tornado risk will likely ramp up again later this morning across south AL and the FL Panhandle along the residual rain-cooled boundary/warm front, and then spread east-northeastward across north FL and GA through the day. Long-tracked, strong tornadoes will be possible with fast moving supercells, in addition to damaging winds and large hail. The severe/tornado risk will spread northeastward into the Carolinas this evening as the cyclone deepens and moves northeastward to the southern Appalachians. There are some concerns regarding the degree of near-surface destabilization with northeastward extent into the Carolinas. However, very strong low-level shear would favor maintenance of any supercells that mature a bit farther southwest in the warm sector, with the risk for tornadoes persisting after dark into SC and perhaps southern NC. Farther south, the band of storms with the cold front will reach south FL overnight, with a continued risk for damaging winds and a couple of tornadoes. ...Central CA coast today... Another strong shortwave trough will move inland today over CA. As the left exit region of the mid-upper jet overspreads the coast and near-surface flow becomes onshore with frontal passage, weak surface-based buoyancy will develop. There will be some potential for low-topped thunderstorms with isolated damaging gusts in this regime. ..Thompson/Cohen.. 01/22/2017